Question

If tan A = tan B and sin A = m sin B, then prove that $\cos {}^{2} A= \frac{m {}^{2} - 1}{n {}^{2} - 1 }$​

Answer 1

$\cos {}^{2} A= \frac{m {}^{2} - 1}{n {}^{2} - 1 }$

Hence, proved.

Please see the above attachment for explanation.